“A group of black-clad protesters has raged through downtown Toronto, smashing windows, vandalizing businesses and burning at least two police cruisers in the heart of the city.

The riots have forced officials to shut down downtown subway stations and close off main streets from traffic.

Only a few blocks from the mayhem, G20 leaders are meeting at the Metro Toronto Convention Centre.

For more than five hours, much of the city’s core has been in a virtual lockdown as heavily armed police periodically clash with protesters.

The violence escalated after a splinter group broke away from a large and peaceful group of protesters who marched ahead of the high-level meetings.

A concert at the Air Canada Centre has been postponed, hospitals in the downtown core have been locked down and the Eaton Centre was also closed.

Toronto Mayor David Miller said at a news conference that the so-called anarchists are simply criminals who are determined to cause as much destruction as possible.

“It was a deliberate act by people who make it their business to commit these acts,” he said.

“Am I angry? Absolutely.”

Miller spoke to reporters at about 6 p.m. local time, nearly five hours after the protest erupted into violence.

Earlier, the black-clad protesters smashed up a police cruiser and smashed its windshield along Queen Street, as other demonstrators hurled bottles and sticks at a solid line of riot police.

As police donned gas masks and mounted units rode into the city’s core on horses, the violent protesters lit garbage on fire and tipped over recycling containers. They also smashed vehicles in and grabbed stones from nearby homes.

News media vehicles were also targeted and vandalized.

Initially, there were reports that police had fired tear gas. However, police said later that no officers had deployed any gas.

Earlier on Queen Street, next to the MuchMusic building, the violent protesters attempted to break southward through a tight line of riot police.

As some in the crowd pelted police with water bottles, officers hit back and pushed the group northward, away from the downtown core.

Three protesters involved in the confrontation suffered injuries. According to reports from the scene, some were bleeding from the head.

Moments later, another standoff occurred a few blocks west, where protesters reportedly tossed sticks at police and chanted “let us go.”

While protest organizers promised a family-friendly demonstration, a splinter group calling itself the “Get off the Fence contingent” has announced plans to break away from the main group and challenge the heavy security cordon around the Metro Toronto Convention Centre, where the G20 summit will begin Saturday afternoon.

In a news release, the splinter group said it plans to continue on to the summit site “to confront the self-proclaimed G20 leaders and the security apparatus that will have occupied our city. We will take back our city from these exploitative profiteers, and in the streets we will be uncontrollable.”

The news release uses the word “militant” a number of times to describe the planned demonstration.

Around 1 p.m., two protesters were arrested near the downtown core and allegedly found with an “incendiary device.” Unconfirmed reports from the scene said the pair was carrying Molotov cocktails.”